1. Field of the Invention
The present invention relates to an imaging unit having an imaging optical system and an image sensor.
2. Description of the Related Art
In recent years, mobile electronic devices which are designed mainly for taking still/moving photographic images, such as digital cameras (still-video cameras) and digital camcorders (motion-video cameras), and other mobile electronic devices which are designed to have the capability of taking such photographic images as a subsidiary function, such as mobile phones equipped with a camera and personal digital assistants (PDAs) equipped with a camera, have become widespread. In these types of mobile electronic devices, it is common to provide the mobile electronic device therein with an imaging unit which is structured such that an image sensor and a photographing optical system, for leading light emanating from a photographic object (object to be photographed) to the image sensor, are accommodated in a hollow housing of the imaging unit.
In this type of imaging unit, it is sometimes the case that a prism which bends an optical path to lead this optical path to the image sensor is installed immediately in front of the image sensor (on the object side). Additionally, in recent years, the downsizing (slimming down) of the imaging unit has progressed, following the progress of the downsizing (slimming down) of the mobile electronic devices, and accordingly, if a prism is used as an element of this type of imaging unit, this prism needs to be miniaturized.
However, if the prism is miniaturized, stray light occurs by reflections caused by side surfaces of the prism, which increases the possibility of such stray light reaching the imaging surface of the image sensor. Therefore, in the case where a small prism is used, a light shield frame for preventing part of the light emanating from a photographic object from traveling toward the side surfaces of the prism needs to be provided on the incident surface side of the prism.
Japanese Unexamined Patent Publication No. 2010-026007 discloses a light shield frame that is provided on the incident surface of a prism.
Whereas, since the aforementioned prism has been miniaturized as described above and also since it is ideal to make the space in the imaging unit which is occupied by the aforementioned light shield frame as small as possible, the light shield frame needs to be miniaturized to produce a slimmed-down imaging unit.
A light shield sheet which can adhere to the incident surface of the prism is known in the art as an example of the light shield frame which is small in size.
However, since it is difficult to adhere a thin and small light shield sheet to the incident surface of the small prism, there is a possibility of the position of adhering the light shield sheet to the incident surface of the prism deviating from a desired position, which may consequently cause stray light to reach the imaging surface of the image sensor.